If a deck really makes creature defense an aspect of its game plan in this format, the subversion of simple "destroy" effects is the very first obstacle that those decks will anticipate. Decks that are just running some creature defense might be affected, but generally creature removal is in there to supplement some kind of game plan, and so getting a creature to survive a wipe might not do everything you need.
So against true creature-control decks, you'll run into Exile, Tuck, Negative Toughness and Bounce, both targeted and untargeted. In fact, this might be close to 100% of the removal you face from them. This is a dead card against that. Being strictly dead, this card actually makes your deck worse against these decks because it doesn't increase your creature density or make your creatures faster at doing their thing.
Against other decks that just happen to have creature removal, they'll have to continue on with their game plan with few or zero ways to get rid of your creature. The problem here is that they see they can't interact with you, and so they go after you, hoping you have no way to interact with them either. If you don't, it's basically a race. And Plate doesn't help you in this race that it caused. You dumped 5 mana into it, used up a card. So unless you have a creature like Kresh whose in-built power enhancements are absolutely enough on their own, an equal-level deck with equal or better draw-power and mana will still beat you, even in the event a third deck doesn't wipe you both out.
So essentially, this is a passive card that seems like it wants to get used in active strategies. Better is to just use active cards with active strategies. Recursion plus Haste is a good example. ETB abilities and self-bounce are another. You want to be able to use your countermeasures actively against decks that don't engage you, and use mostly creatures that give you value even when they die.
While I agree with just about everything you said, I think everyone should also keep in mind that Indestructible goes beyond just 'wrath-prevention' and also happens to make for extremely good blockers and/or fearless attackers.
These days, I only play it in Damia and Kaalia, where protecting the commander is vital.
I will echo this. It's generally best in decks that either a) Wrath a lot(Destroy wrath of course, not Terminus or Hallowed Burial) or b) Have a general that needs to be out for multiple turns. Or both.
Right now out of my (4) decks it's only in my Kresh deck, but it's used to good effect there.